Deprecate Buffer#trim{Start,End}

Deprecate `Buffer#trimStart` and `Buffer#trimEnd` in favour of `Buffer#dropInPlace` and `Buffer#dropRightInPlace`, which are more consistent with the rest of the API.

Author: NthPortal

library/src/scala/collection/mutable/Buffer.scala

@@ -119,17 +119,16 @@ trait Buffer[A]
  * @param n the number of elements to remove from the beginning
  * of this buffer.
  */
- def trimStart(n: Int): Unit = remove(0, normalized(n))
+ @deprecated("use dropInPlace instead", since = "2.13.4")
+ def trimStart(n: Int): Unit = dropInPlace(n)
 
  /** Removes the last ''n'' elements of this buffer.
  *
  * @param n the number of elements to remove from the end
  * of this buffer.
  */
- def trimEnd(n: Int): Unit = {
- val norm = normalized(n)
- remove(length - norm, norm)
- }
+ @deprecated("use dropRightInPlace instead", since = "2.13.4")
+ def trimEnd(n: Int): Unit = dropRightInPlace(n)
 
  def patchInPlace(from: Int, patch: scala.collection.IterableOnce[A], replaced: Int): this.type